Polymer Brush Functionalized Polyacrylonitrile Fiber Membranes for Enhanced Adsorption of Metal Ions

Precious metal recovery from secondary resources is essential due to their limited natural abundance and growing industrial demand. Polyacrylonitrile (PAN)-based fiber membranes have gained significant attention for their high surface area and porosity, but their inherent adsorption capabilities for precious metal ions remain suboptimal. In this work, we present a strategy for enhancing the adsorption performance of PAN fiber membranes by functionalizing their surface with polymer brushes. Using electrospinning, PAN fibers were first fabricated, followed by alkaline hydrolysis to produce hydrolyzed PAN (HPAN) membranes. The membranes were then grafted with branched polyethylenimine (bPEI) and methyl isothiocyanate (MITC), resulting in HPAN-bPEI and HPAN-bPEI-S membranes. The incorporation of polymer brushes significantly enhanced the interaction between the fibers and Au(III) and Ag(I) ions, leading to a remarkable increase in adsorption capacity. The HPAN-bPEI-S membrane exhibited an outstanding adsorption capacity of 232.4 mg/g for Au(III). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic models, suggesting a monolayer adsorption mechanism. Furthermore, the modified membranes demonstrated excellent recyclability, retaining over 85% of their initial adsorption capacity after five adsorption-desorption cycles. This work demonstrates the potential of polymer brush-functionalized PAN fiber membranes as high-capacity adsorbents for the efficient adsorption and recovery of metal species from water, offering a sustainable solution for environmental remediation and industrial applications.